CHM 30 Chapter 2: Atoms, Ions, and Molecules - Vocabulary

Vocabulary flashcards covering key concepts from atomic theory, isotopes, periodic table, nomenclature, ionic/covalent bonding, acids, and hydrates.

Atom

The basic unit of matter; in modern terms, a nucleus of protons and neutrons surrounded by electrons.

Electron

A negatively charged subatomic particle discovered by J.J. Thomson; a key component of the atom.

Cathode ray

A beam of electrons produced in a vacuum tube, used to study electron properties.

Mass-to-charge ratio

The ratio m/e for electrons; used in Thomson’s experiments to deduce negative charge.

J.J. Thomson

Physicist who discovered the electron and proposed the plum pudding model of the atom.

Plum pudding model

Thomson’s early atomic model with a positively charged 'soup' containing embedded electrons.

Nucleus

The dense, positively charged center of an atom; Rutherford showed atoms are mostly empty space.

Rutherford

Physicist who conducted the gold foil experiment, proving the existence of a small, dense nucleus.

Isotopes

Atoms of the same element (same Z) with different numbers of neutrons, hence different mass numbers (A).

Mass number (A)

Total number of protons and neutrons in a nucleus.

Atomic number (Z)

Number of protons in the nucleus; identifies the element.

Nuclide notation (A Z X)

Notation where A is mass number, Z is atomic number, and X is the element symbol.

Atomic mass unit (amu)

Unit for atomic/subatomic masses; 1/12 the mass of carbon-12.

Atomic weight / average atomic mass

Weighted average mass of an element’s isotopes, based on abundance.

Periodic table

Organization of elements by increasing atomic number with recurring chemical properties.

Period

A horizontal row in the periodic table.

Group

A vertical column in the periodic table; elements in a group have similar properties.

Alkali metals

Group 1 metals; highly reactive (e.g., Li, Na, K).

Alkaline earth metals

Group 2 metals; reactive metals (e.g., Be, Mg, Ca).

Lanthanide series

Elements 57–71; inner transition metals, often shown separately in the periodic table.

Actinide series

Elements 89–103; inner transition metals, many radioactive.

Binary molecular compound

A compound formed from two nonmetals; named with prefixes and the -ide ending on the second element.

Prefixes (mono-, di-, tri-, tetra-, penta-, hex-, … )

Greek prefixes used to indicate the number of atoms of each element in binary molecular compounds; first element typically lacks mono.

-ide suffix

Suffix added to the second element in binary molecular compounds.

Ionic compound

Compound formed from cations (metals) and anions (nonmetals or polyatomic ions) that typically forms a lattice.

Formula unit

The lowest whole-number ratio of ions in an ionic compound.

Common ions

Ions that frequently appear in compounds (e.g., Na+, Cl-, NO3-, OH-, SO4^2-, CO3^2-).

Polyatomic ion

A charged group of two or more atoms that acts as a single unit (e.g., NO3^-, SO4^2-).

Roman numeral (in ionic naming)

Indicates the charge of a metal cation when it has multiple possible charges (e.g., Fe2+, Fe3+).

Binary ionic compound naming

Name the cation (with Roman numeral if needed) then the anion (ending in -ide or a polyatomic ion); e.g., MgBr2 → magnesium bromide.

Copper(I) oxide

Copper in the +1 oxidation state bound to oxide; formula Cu2O.

Copper(II) oxide

Copper in the +2 oxidation state bound to oxide; formula CuO.

Acids

Molecular compounds that release H+ (protons) in water; typically start with H in their formula.

Binary acids

Acids formed from hydrogen and another element; named with hydro- prefix and -ic acid (e.g., HCl → hydrochloric acid).

OxOacids

Acids containing hydrogen, oxygen, and another element; named by the oxoanion with -ic or -ous suffix (e.g., NO3^- → nitric acid).

-ate vs -ite

In oxoacids, -ate becomes -ic acid and -ite becomes -ous acid, with the same overall charge. Samples: NO3^- → nitric acid; NO2^- → nitrous acid.

Hydrates

Compounds with water molecules bound in the crystal; written with a dot (e.g., CoCl2·6H2O).

Hexahydrate

A hydrate with six water molecules per formula unit (e.g., CoCl2·6H2O).